A teenager has been sentenced to life in prison for his role in a plot to lure men to a non-existent cattle farm with fake job offers and rob them.

A judge sentenced 17-year-old Brogan Rafferty on Friday in Ohio on his conviction for aggravated murder and attempted murder.

Authorities said Rafferty lured four victims with bogus job vacancies on the classified advertisements website Craigslist to the non-existent cattle farm in southeast Ohio.

His alleged accomplice Richard Beasley, 53, allegedly shot and killed three of the men. A fourth victim was shot in the arm but survived.

During the trial, prosecutors painted Rafferty as a "student of violent crime" who was a willing participant in the three murders while the defence argued he was acting under the duress of Beasley, a self-styled chaplain depicted as a mentor.

The man who survived, 49-year-old Scott Davis of South Carolina, had testified as the prosecution's star witness, identifying Rafferty as Beasley's accomplice.

Mr Davis told the court he had responded to a Craigslist advertisement to work as a farmhand. He met a man calling himself "Jack" for breakfast before driving to an isolated Noble County farm.

Prosecutors say that "Jack" was actually Beasley, and that he urged Mr Davis into a wooded area to look for farm equipment.

Mr Davis said he heard a gun cock and turned around to find himself face to face with a handgun.

He said he pushed the weapon aside, was shot in the arm and fled as "Jack" fired at him. Mr Davis said he eventually climbed to a hilltop, found a house and asked to call police.

Authorities said all the men were targeted because they were older, single and out of work with backgrounds that made it unlikely their disappearances would be noticed right away.

All the victims were robbed of items including personal possessions, a truck and a weapon, prosecutors said.

Rafferty had testified that he did not want to be involved in violence and said he went along with the plan only because he feared for his life.

Beasley has pleaded not guilty and could face the death penalty if convicted at his separate trial.